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Next Nanotechnology

Coherence control in graphene for photonic networking and quantum information storage

Awais Tabassum, Bin Li, Saad Shaheen, Waqar Yousaf, Manlu Liu

Published May 16, 2026• 0 citations
Publisher

Abstract

Landau-quantized graphene (LQG) offers a magnetically controlled platform for manipulating coherent inter-Landau-level transitions of Dirac fermions. Such a platform provides compact control of terahertz and infrared photonic signals. Here, a closed-form susceptibility expression is derived using the density-matrix approach, where the real part of the susceptibility describes dispersion and the imaginary part describes absorption or gain. The numerical results show that tuning the control field modifies the probe response from a dispersive resonance regime to a transparency window and a gain-assisted response. The calculated group-index variation, approximately from 0.6 to 1.7, enables broad modulation of the probe group velocity, ranging from about 1.8 × 10 8 m/s to 5.2 × 10 8 m/s . The reduced-absorption region indicates an electromagnetically induced transparency response suitable for controlled probe-field transmission. Distinct spectral features are also observed in the absorption coefficient and electron energy-loss spectrum (ELS), indicating selective energy transfer near the LQG resonance and potential relevance for THz/IR modulation. In addition, the frequency-selective and sign-reversible photon-drag response suggests detuning-controlled optical momentum transfer. These tunable responses within the linear regime support LQG as a reconfigurable medium for quantum optical transport, synchronization, pulse routing, buffering, and chip-scale THz photonic interfaces.

DOI
10.1016/j.nxnano.2026.100520

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Landau-quantized graphene (LQG) offers a magnetically controlled platform for manipulating coherent inter-Landau-level transitions of Dirac fermions. Such a platform provides compact control of terahertz and infrared photonic signals. Here, a closed-form susceptibility expression is derived using the density-matrix approach, where the real part of the susceptibility describes dispersion and the imaginary part describes absorption or gain. The numerical results show that tuning the control field modifies the probe response from a dispersive resonance regime to a transparency window and a gain-assisted response. The calculated group-index variation, approximately from 0.6 to 1.7, enables broad modulation of the probe group velocity, ranging from about 1.8 × 10 8 m/s to 5.2 × 10 8 m/s . The reduced-absorption region indicates an electromagnetically induced transparency response suitable for controlled probe-field transmission. Distinct spectral features are also observed in the absorption coefficient and electron energy-loss spectrum (ELS), indicating selective energy transfer near the LQG resonance and potential relevance for THz/IR modulation. In addition, the frequency-selective and sign-reversible photon-drag response suggests detuning-controlled optical momentum transfer. These tunable responses within the linear regime support LQG as a reconfigurable medium for quantum optical transport, synchronization, pulse routing, buffering, and chip-scale THz photonic interfaces.
This article presents an exclusive study of the linear and higher-order susceptibilities, as well as the reduction in group index of a weak probe pulse in a three-level Landau-quantized graphene (LQG) system, under the influence of a strong control field, utilizing the phenomenon of electromagnetically induced transparency. The influence of the magnetic field on the higher-order nonlinearities (Kerr, quintic, and septic) leads to observable changes in amplitudes and shifts in probe frequencies. The LQG system exhibits giant values for these nonlinear susceptibilities with χ(3), χ(5), χ(7) reaching magnitudes approximately ∼10−18m3/V2, ∼10−30m5/V4, and ∼10−42m7/V6, respectively, in the mid-infrared range. The magnetic field also induces asymmetric absorption peaks and modifies dispersion profiles. The study also demonstrates a reduction in the group velocity of the probe, under the effect of the magnetic field, by 1000-fold compared to the speed of light in free space. These giant higher-order nonlinearities, coupled with significantly reduced group velocity, suggest that the LQG system is a quick responder, revealing it as an excellent candidate for terahertz modulation. This also highlights the potential of the system as a promising material for generating and detecting coherent nonlinear signals in the mid-infrared range.
Graphene nanomaterials exhibit excellent optical properties when interacting with electromagnetical fields, which plays an important role in a wide range of applications such as optical communications, optical storage and other fields. Based on the electromagnetically induced transparency (EIT) effect, we investigate control of slow light in the Landau quantized graphene system with different three-level and four-level coupling schemes. Utilizing the EIT effect, group velocity of the probe fields can be significantly reduced and well controlled by manipulating Rabi frequencies and detunings of the coupling lasers as well as probe detuning. Furthermore, probe light with different frequencies can even be controlled in different EIT windows in the graphene system with the four-level scheme, which may find applications in signal selection and discrimination. This work can provide reference for the design of graphene-based quantum devices and have potential applications in optical communications and optical quantum information processing, etc.
Abstract The optical properties of a weak probe light by applying coupling fields in Landau-quantized graphene nanostructure is investigated. In this structure the electromagnetic field of terahertz-infrared radiations interfere with the electromagnetic field of the short-wavelength probe field and this effect changes the absorption and dispersion characteristics of the probe field. The linear dynamical properties of the graphene by means of perturbation theory and density matrix method are discussed. We show that the group velocity of a light pulse can be switched from superluminal to subluminal or vice versa by controlling the coupling field’s intensities and relative phase of the applied fields. Therefore, this model can be used as an all-optical switch which is suitable for next generation of future all optical quantum communicational system and networks.
We theoretically investigate dynamical control of light slowing within the induced transparent window, e.g., in near-infrared frequencies, in electromagnetically induced transparent (EIT) metamaterials loaded by low-lossy graphene. Coupling with graphene enables distinctive optical responses of the "bright" and "dark" resonators in EIT metamaterials, rendering a switching of the transparent window and a modulation on light dispersion. Optical performance of the transparent window manifests continuous tuning as the graphene doping level changes. We show that the active modulation on optical properties of the transparent window enabled by low-lossy graphene is distinctive either by passively adjusting the interspacing between the building blocks of EIT metamaterials, or active tuning by high-lossy graphene. Furthermore, we report that the group refractive index can be in situ tuned dynamically over a broad range, e.g., ∼2 orders for near-infrared frequencies, together with absorption maintained at a level similar to that of the unloaded structure. Our study offers new possibilities towards chip-scale devices, such as active optical switching, filtering, and data storing.
Abstract We investigate theoretically the controlled magneto-optical Faraday rotation (MO-FR) through graphene-based metasurfaces placed on electromagnetically induced transparency (EIT) substrate at terahertz (THz) frequencies. MO-FR and transmission of the probe light are studied by changing the electric field that manipulates the group index of the substrate. The MO-FR can be controlled and enhanced by varying the periodic width of graphene ribbons. The polarization plane of MO-FR changes with 180 degrees while increasing the probe field detuning through the EIT substrate. The zero-crossing of MO-FR shifts to higher THz frequencies with increasing the magnetic field. The transmission of the probe light pulse at THz frequencies is investigated with the probe detuning and the applied magnetic field.
This work studies the absorption spectrum of a two-level quantum emitter coupled to a photonic environment modified by the plasmon modes of a graphene nanodisk. Using macroscopic quantum electrodynamics and a Lorentzian mapping, the system is described within an effective cavity quantum electrodynamics framework. Analytical expressions are derived for the linear susceptibility, and three distinct spectral regimes are identified. In vacuum induced transparency, destructive quantum interference opens a narrow transparency window in the absorption spectrum. In vacuum Rabi splitting, coherent energy exchange between the emitter and the plasmonically modified photonic mode produces a well-resolved doublet. When plasmon losses are large, the required interference is suppressed, leading to the absence of induced optical transparency. It is shown that the transitions between these regimes are strictly determined by the exceptional points of the system's effective non-Hermitian Hamiltonian, and a complete phase diagram is provided as a function of the emitter-nanodisk distance and the free-space decay rate. The results highlight graphene nanodisks as a highly tunable platform for the dynamic control of quantum interference, offering potential applications in reconfigurable nanophotonic spectral switching and transparency-window engineering.